Iran veered closer to being slapped with tough new international sanctions on Monday when its president refused to stop enriching uranium and the UN nuclear watchdog warned of a "stalemate" with the country. President Mahmoud Ahmadinejad said Teheran was ready to talk with world powers about unspecified "global concerns" - but he insisted his government would neither halt uranium enrichment nor negotiate over its nuclear rights. "From our point of view, Iran's nuclear issue is over," Ahmadinejad declared in Teheran. "We will never negotiate Iran's undeniable rights." In Vienna, International Atomic Energy Agency chief Mohamed ElBaradei urged Teheran to "substantively reengage" with the international community and clear up questions about its nuclear ambitions once and for all. "Iran needs to respond fully to all the questions raised by the agency in order to exclude the possibility of there being military dimensions to its nuclear program," ElBaradei told the IAEA's 35-nation board of governors on Monday. This week's meeting of the IAEA board in Vienna, and the upcoming UN General Assembly session, could set the stage for a toughening of sanctions against Iran for its continued defiance of Western demands that it suspend uranium enrichment. US President Barack Obama and European allies have given Iran until the end of the month to take up an offer of nuclear talks with six world powers and trade incentives should it suspend uranium enrichment activities. If not, Iran could face harsher punitive sanctions. But Ahmadinejad ruled out negotiations on his country's nuclear program while saying he was willing to discuss other international issues in public with US President Barack Obama. At his first formal press conference since his June 12 reelection, Ahmadinejad said he didn't recognize deadlines for talks on Teheran's nuclear plans. At the same time, he said: "We are ready to discuss world issues with the US president in the presence of mass media. The time of hidden agreements is over, and television debates are the best way." Ahmadinejad, who won a second four-year term in the disputed election, urged the US to change its approach to relations with Iran, saying the Persian Gulf nation would welcome such a development. He said Iran was ready to discuss global issues with Obama. Ahmadinejad said he and an Iranian delegation would attend the General Assembly session in New York later this month. "We protest the current situation," he added, after criticizing the way the UN was run. The US, China, Russia, France and the UK - the five permanent members of the UN Security Council - and Germany, met on September 2 to discuss an offer for direct talks with Iran on its atomic work. Defense Secretary Robert Gates said on July 27 that the US would seek support for "a much tougher position" should Teheran fail to revive nuclear talks in coming weeks. Iran would present updated proposals to the Security Council group responding to Western concerns about Iran's nuclear program later this week, Ahmadinejad said. Iran was ready for talks about the peaceful use of nuclear energy for all countries, as well as organizing worldwide nuclear nonproliferation, Ahmadinejad said. His press conference in Teheran was carried live by state television. His defiant statements were made as the 35-nation board of the International Atomic Energy Agency convened in Vienna to discuss Iran and Syria this week, with IAEA head ElBaradei urging the Islamic Republic to "substantively reengage" with the international community. Israeli officials, however, have low expectations of the meetings, saying it was unlikely any resolutions would be passed. One senior government official said that the board of governors meeting would be made up mostly of speech-making, but no practical decisions. He said no decisions were expected until it became clear whether Iran would seriously take up Washington's engagement offer. The G-20 meeting in Pittsburgh, Pennsylvania, on September 24, as well as the upcoming UN General Assembly session, could - if Iran did not respond positively to Washington's offer - set the stage for a toughening of sanctions. ElBaradei on Monday acknowledged that Iran had provided IAEA inspectors access to a research reactor at Arak and had tightened security at its main nuclear facility in the southern city of Natanz. But he said the Islamic Republic was still enriching uranium, which can be used for nuclear fuel or - if enriched to a high enough level - can produce fissile material for a warhead. "On all other issues relevant to Iran's nuclear program... there is stalemate," ElBaradei told the IAEA board. "Iran has not suspended its enrichment-related activities or its work on heavy water-related projects, as required by the Security Council, nor has Iran implemented the Additional Protocol," which would open its nuclear facilities to unannounced and more intrusive inspections. "It is essential that Iran substantively reengage with the agency to clarify and bring to closure all outstanding issues," he said. "Iran needs to respond fully to all the questions raised by the agency in order to exclude the possibility of there being military dimensions to its nuclear program," he added. Muhammad Saeedi, deputy head of the Atomic Energy Organization of Iran, said his country had provided the IAEA with all the information it needed and that it was now up to the agency to act. "In our view, we believe that the agency should finalize the outstanding questions," Saeedi said. He said Iran had also "cooperated widely" with the IAEA to improve safeguard measurements at Natanz and "voluntarily" provided UN nuclear inspectors access to its Arak site. ElBaradei sharply criticized recent media reports suggesting that his office had held back some of the intelligence it had collected on Iran. He said he was "dismayed" by the notion, and denounced the reports as "politically motivated and totally baseless." Israel intimated that the IAEA was hiding some of its findings on Teheran's weapons program in its response to the IAEA report released some 10 days ago. "It is a harsh report, and yet it does not reflect all the information known to the IAEA regarding Iran's efforts to continue to pursue its military program, its ongoing attempts at concealment and deception, and its lack of cooperation with the IAEA and the demands of the international community," Israel said in a Foreign Ministry statement at the time. ElBaradei also criticized Syria for failing to disclose details about a desert site bombed by Israel in September 2007. "Syria has not cooperated with the agency to confirm Syria's statements regarding the nonnuclear nature of the destroyed building on the Dair Alzour site, nor has it provided the required access to information, locations, equipment or materials," he said.